Transmitter cell



i9 1939- A. E. wooDRuFF E'r Al. 2,184,064

TRANSMITTER ELL Filed Sept. 3, 1937 PHC-3.2

FBC-M INVENTORS- ALBERT awooDmJFF ALBERT RHORLAQHER BYMUa/,M'mm%m @of ATTORNEYS Patented Dec. 19, 1939 vsmi? sentant-p les aisance rrnansmrraa para.

Albert E. wonend, oak rai-k, and Alberi F. nprlacher, Chicago, Ill., assignors to Associated Electric Laboratories, Inc., Chicago, Ill., a corporation of Delaware Application September 3, 1937, Serial No. 162,253

The present invention relates to transmitter cells and more particularly to cells of this character which are, inv operation, Aresponsive "to ree ceived mechanical vibrations as contrasted to 5 transmitter cells of conventional form which respond to sound waves transmitted thereto.'

The type of transmitter cell noted, which usually comprises a vibratory structure including a diaphragm directly exposed to the mechanical lll vibrations representing theintelligence or speech to be transmitted, possesses certain desirable operating characteristics when used for the transmission of sech by wire or radio from an area in which the background noise is exceptionally 11d high. One such application which readily Asug`- gests itself relates to `.the'transmission of speech by radio from a radio transmitter carried in the cockpit of an airplane. When ya microphone cell of this character is used for the transmission of 2@ speech, the vibratory diaphragm thereof is usually supported directly against the throat of the wearer or user so that it respondsto the muscular vibration of the wearers throat during speech.

By this arrangement, the background noises are w substantially eliminated and only the mechanical vibrations of the diaphragm caused by the speech of the user are transformed into electrical undulations for modulation on the carrier transmitted from the associated radio 'transmitting s@ apparatus. Although possessing the advantages noted, the mechanically responsive transmitter cell has not' been extensively used in applications of the type just referred to for the reason that the previously known cells of this form have not 35 been characterized by any substantial degree of sensitivity, as regards the response characteristic thereof, and have been of a cumbersome and relatively expensive construction.

y It is an object of the present invention, theredll fore, to provide an improved transmitter cell of Ithe character brieflyv described above which is highly responsiveto mechanical vibrations trans- 55 portion of the cup-shaped member and the base 3 claims. v(ci. 11s- 122) member is av structure for retaining therein a granulated carbon pile, which structure comprises a pair of rigid, cup-shaped electrodes, one of which is supported by the base member, and the other of which is oppositely disposed with 5 respect to theiirst electrode and is connected to Athe bottom portion of the cup-shaped member for vibration therewith. This structure also includes a flexible member connecting the oppositely disposed rims ofthe two electrodes to'complete the 10 enclosure for the carbon piln Various other improved features of the structure-pertain to the construction and compositionv of the electrodes, the manner in which they are supported on or connected to their'respectlve supporting mem- 15 bers, the manner in which the diaphragm portion`of the cup-shaped member is formed and the manner. in which the cup-shaped member is secured to the base member. o

The novel features believed to be character-'20 istic 'of the invention are set forth with particularity in the appended` claims. The invention itself, however, both as to its organization and method of operation, together with-further objects and advantages thereof, will best be understood by reference to the specification taken in connection with the accompanying drawing, in which Figure 1 is a cross sectional viewillustrat- `ing a transmitter cell constructed and arranged in accordance with thev present invention. Fig. 2 is a plan view of a portion of the cell shown `in Fig. 1, and liig. 3 is an exploded view illustrating the manner of assembling the elements of the cell as shown in Figs. l and 2.

Referring now to the drawing, there is illus- '35 trated a transmitter cell having embodied therein the features of the present invention as comprising a cylindrical base member .I0 constructed of insulating material,.a cup-shaped member Il,

.f circular contour and having an outer diameter, 40

equal to the outer diameter of the base member III,l and a structure indicated generally at l2 for retaining therein a granulated carbon pile, not shown. The bottom portion of the base member lil is provided with an annular depression i3 45 which is adapted to accommodate the end of a flexible supporting member, not shown, forming a part of an improved microphone supporting assembly which is described and claimed in the present applicants' co-pending application S. N. 50

162,252, filed Sept. 3, 1937. The narrowed ,lengthl A of the flexible supporting member rests in a 'slot il extending from the depression I3 exteriorly of the base member Ill.v For thepurpose of retaining the end of the flexible supporting memon the base member I by means comprising,

ber within the depression I3. there is provided a cover plate I5 which is adapted to be mounted screws I6 threaded into` metal inserts I1 molded into the base member Il.

The rim portion of the side wall of the cupshaped member Il is cut flat across so that the surface thereof engages at substantially all points thereof vthe upper flat sealing. surface of the base member I0. Integral with and extendf member to prevent the same from being crushed i in character.

during rough handling and thereby enhance the ruggedness of the cell. In yaccordance with one feature of the present invention, thesurface of the rim of the member II and-the inner wall surfaces thereof are secured to the oppositely disposed surfaces of the base member I0 lby bonding the same thereto with cement. `In` this-connection, it is pointed out that the word cemen is used in a generic sense to denote, any form of compound having the necessaryeadhesive qualitl'esrrmly to hold the member II secured to the base member Ill. This.. method of attachment possesses distinct advantages in that it 4insures an extremely tight joint which prevents -the entrance of foreign matter interiorly of the cliamber formed between the members I0 andv I I, it enhances the pleasing appearance of the cell, and

it eliminates any possibility of the diaphragm.-

forming an integral portion of the memb rf II, being affected in its operation by the atta ent of this member tothe base, member |40.

The cup-shaped member II is provided with a thin walled bottom portionor 'end wall Il adapted to function as a vibrating diaphragm responsive to the audio-frequency muscular vibrations of the body of a user when the device is attached to the throat of a wearer or user.. This portion I8 has extending inwardly therefrom a projection I9' forming a part of the connection between the diaphragm portion of the member II and one electrode -of the structure I2. It has been found Athat the responsivenessiof they cell is considersubstantially from they center of this portion and approaching the side walls'of the cup-shaped member II in the manner illustrated. In thisY connection, itis pointed out that the member II is ypreferably constructed of cellulose'acetate material which, ras is well known, is transparent Such material is welLsuited for this particular use in that the ratio between its elasticity and massis relatively high and it is thus possessed of the one characteristic which is highly desirable in a diaphragm material. Moreover, this material is practically indestructible when subjected to the handling accompanying ordinary usage of the cell.

portion 22 spun over at its upperedge-to seat vvelectrodes I9 and 20. This opening is plugged --completed by the provision of a flexible member against a flexible circuit element 23 having an annular portion 23' encircling the walls of the insert piece 2l and seated on the upper portion of \the electrode t9. Extending within the walls of the insert 2| is a projection which juts down- 5 ward from the bottom or diaphragm portion I8 of the member Il. This projection is providedl at its lower end with a flat surface which is bonded to theoppositely disposed flat surface forming the bottom of the Walled portion 22 of the insert piece 2L Preferably, such bonding is accomplished through the use of cement or glue having the requisite adhesive qualities rigidly to secure the electrode I9 to the portion Il of the member II for vibration therewith. The oppositely disposed electrode 29 is seated in a depression provided in the centralportion of the base member I0 and conforming in contour to the contour of the outer surface of the electrode. This last-mentioned electrode, like the electrode I9. is provided with an opening coinciding with an opening formed in the center of theba'se member III and is secured to the base member by means comprising a hollow metal insert piece 24 extending throughY the coincidental openings noted. This insert piece 24 is provided with a flange 24' which abuts the surface adjacent the upper edge of the opening in the electrode 20 and the edge of the opposite end thereof is spun pver to engage the surface adjacent the', lower edge of the' opening in the member I0. 'Ihe opening through the insert piece 24 serves for the introduction of granulated carbon into the enclosure formed bythe two oppositely disposed by a`cap 25 seated in'a circular depression axially coincident with v'the vopening in the insert piecev 24 and clamped in position by a projection from the bottomvplate I5. vThe structure I2 is 26 constructed of paper or like material and having a number of reversely folded sections so constructed as to form a lbellows having itsv opporims of the electrodes I9 and 20. By this arrangement, the vibratory structure includlng the bottom portion I9 of the memberll and the electrode I9 is left free to vibrate in accordance with the mechanical vibrations Vimpressed thereon, thereby to vary thefresistance oi' the carbon pile enclosed within the structure I2 without an excessive amount of damping.

Each of the two electrodes I9 and 20 is preferablyconstructed of a compressed mixture of granulated carbon and a suitable binder material. As thus formed, the electrodes are not susceptible of permanent distortion due to mechanical forces impressed thereon during rough handling. Moreover, the carbon constituent of the electrodes enhances the electrical contact between each of lthe electrodes and the granulated carbon in the carbon pile', thus improving the electrical characteristics of the cell.

The circuit conductor 23 terminating at the electrode I9 is connected to ametal insert piece 2.1 molded in the base member I0, which insert piece forms one of the terminals of the ,cell Similarly, the stationary electrode 29 is connected, by means comprising a conductor element 29, to an insert piece 28 molded into the base member I0. The element 29 is provided `with an annular portion 30 which encircles the electrode 20 and is clamped between the outer 7 edge of the insert piece 2d is then spun rover,A

electrode Eil is iirst positioned in its accommodating depression provided in the base member It,

with the annular portion 30 of the conductor element 29 encircling the same, following which the metal insert piece 2N is extended through the coincident openings provided in this electrode and the base member it. The inserted leading thereby rigidly to secure the`electrode 2|) and the element 29 in position. Thereafter, one edge of the exible member 26 is cemented to the rim of the `electrode 20. The insert piece-2 l, theV electrode i9, and the conductor 23fare assembled in a similar manner by. first inserting the metal insert piece 2l through the accommodating opening provided in the electrode I9 and the circular opening in the conductor element 23, andthen spinning over the edge of the walled portion 22 of this piece., With the last-mentioned assembly operation performed, the remaining exposed edge oi the' flexible memberj is cemented to the rim of the electrode I9 and the two conductors 23 and 29 are soldered to the respective terminal insert pieces 2l and 28. In order to cement or bond the projection i9 to the bottom oi the walled portion 22 of the insert piece 2i, a tool is inserted through the opening in the' insert piece 24 and placed against the flanged end of the insert 2li. Thus, theflat surface of the projection i9 may be pressed firmly against the engaging surface of the insert 2| until the ,cement provided for bonding these two velements together has completely set. Also, the at rim surface of the member il is cemented or bonded to the iiat surface of the base member I0 in order to provide a seal therebetween. Thus, a transmitter cell is provided which is not only thoroughly reliable in operation but is of extremely rugged construction.

While there has been describedA what is at f present considered to be the preferred embodiment of the invention, it will be understood that ing and a thin end wall adapted-to function as a vibrating diaphragm responsive to the audiofrequency muscular vibrations of the body of a wearer, the thickness of the end wall of saldcupshaped member decreasing gradually toward .the side wall thereof and being the least jat points displaced from the center thereof and approaching the side wall of said cup-shaped member,

and a structure positioned between the end wall of said cup-shaped member and said base member for retaining. therein a granulated carbon pilel said strucire including an electrode supported by said base member, and an electrode 'connectedeto the end wall of said cup-.shaped ,o memberA for vibration therewith.

2 A transmitter cell comprising, in combination, a base member provided with a sealing surface, a cup-shaped member including a side wall provided with a rim secured and sealed to the sealing surface of said'fbase member, said cupshaped member having a thin end wall provided with a continuous outer surface and adapted to function as a vibrating diaphragm responsive to the audiofrequency muscular vibration of the body of a wearer, the end wall of said cup-shaped fmember carrying an integral and inwardly extending projection substantiallyat the center thereof, and a structure positioned between the end wall of said cup-shaped member and said base member for retaining therein a granulated carbon pile, said structureincluding an electrode supported by said base member, a second electrode .having an opening therein, and an insert piece extending through said opening, said insert projection carried by the end wall of said cupshaped member being arranged within the hollowed portion of said insert' piece and being bonded to said insert piece by cement, thereby to connect said second electrode to the end wall of said cup-shaped member for vibration therewith. f

L'A transmitter cell comprising, in combination, a base member, a cup-shaped member having its rim bonded to the surface of said base said base member having an opening therein, and

a structure positioned between the bottom portion of said cup-shaped member and said base member for retaining therein a granulated carbon pile, said structure including a pair of electrodes, said electrodes each having an opening therein and being composed of a compressed mixture of granulated carbonvand a binder material, a vhollow metal insert piece extending through the opening in said base member and the opening in one of. said electrodes, said-insert piece having a flange at one edge and being spun over at its other edge to secure said one electrode to said base member, the opening in-said insert piece serving for the introduction of granulated carbon into said structure, and a second metal insert piece extending through the opening in the second of said electrodes, said second insert piece having a ilangeabutting the inner surface `of said secondV electrode and' a walled-portion spun over the outer edge of the opening throughwhich it extends, said projection extending within the walled portion of said second insert piece and being bonded thereto by cement, thereby to connect said second electrode to the bottom portion of said cup-shaped member for vibration" tnerewmi. a

maar E. 'WOODRUFF'.

-ALBERT F. HORLACm. n 

